The invention relates to a brake booster of tandem type, and in particular, to the positioning of various members which secures passages between individual pressure chambers.
A brake booster of tandem type known in the prior art has a construction including a pair of power pistons which are disposed within and serve as partitions in an enclosed shell, a valve body internally housing a valve mechanism, and a center body having a path formed therein which communicates with a passage within the valve body, all of which are integrally connected together by being held between a hub which extends through axial portions of these members and a nut which is threadably engaged with the humb. In conventional construction of tandem brake booster, the peripheral surface of the hub and an opening formed in the front power piston through which the hub extends are both formed in polygonal shape such as hexagonal shape for engagement therebetween.
When the outer surface of the hub and the opening in the front power piston are hexagonal in configuration, it is possible to achieve an engagement between the piston and the hub at an angular position which is angularly displaced 60.degree. from its design position. Accordingly, before these members are connected together, it is necessary that their positions be confirmed so that a path formed in the piston communicates with a path formed in the center body.